JP2742131B2 - Manufacturing method of ultraviolet shielding circuit board - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a circuit laminate excellent in ultraviolet shielding properties.

[Conventional technology]

In the printed wiring board, a solder resist is usually formed on the outermost conductive pattern layer to prevent a solder bridge between conductors at the time of soldering or to permanently protect the conductive pattern.

The solder resist is formed by a screen printing method or a photo printing method using a photosensitive resin. Conventionally, screen printing methods have been widely used, but as electronic components have become smaller and smaller, the mounting density on printed wiring boards has increased, and screen printing methods have become practical in terms of precision and workability. Sex is getting smaller. Therefore, instead of the screen printing method, a photographic printing method using a negative or positive mask using a photosensitive resin (photoresist) has come to be performed.

However, in the photo printing method, when the photoresist is simultaneously exposed on both sides of the double-sided printed circuit of the laminated board, the light transmitted through the photoresist at the time of exposure is further transmitted into the laminated board, and the photoresist on the opposite side is also exposed. As a result, a phenomenon that the accuracy of the solder resist, which is the original purpose, becomes insufficient has become known, and peeling of the solder resist at the time of development has frequently occurred. In particular, it is known that the light transmittance is large when the thickness of the laminate is 1.6 mm or less.

For this reason, the thickness of the photoresist is large (50-80 μm)
Using a photoresist film
As described in JP-A-34140, a laminate using a polyimide-modified resin as a base material serving as the outermost surface of the laminate is used. However, when the thickness of the photoresist is increased, an extra curing time is required after exposure and development in order to sufficiently exhibit the performance as a solder resist. On the other hand, the use of a polyimide-modified resin for a part of the laminate increases the cost and has a disadvantage that the prevention of light transmission is still insufficient. In order to eliminate these drawbacks, a method has been considered in which a light-shielding substance is contained in the laminate to prevent light transmission (Japanese Patent Application Laid-Open No. 54-32769).

The present inventors have studied various light shielding substances, and found that among organic ultraviolet absorbers, those having a specific ultraviolet wavelength absorption region are effective in preventing light transmission,
Increasing the content in the laminate has disadvantages such as a decrease in performance as a printed circuit board, such as discoloration due to heating, a decrease in solvent resistance, and thermal deterioration of various performances.

Further, when the content is reduced, a laminate having a thickness of 1.2 mm or less has a disadvantage that the effect of preventing light transmission is small. In addition, it has been found that inorganic ultraviolet shielding agents are also particularly effective for oxides.However, when an amount capable of preventing light transmission is blended into a resin and then applied and impregnated, the difference in specific gravity between the resin and the inorganic oxide results. However, it is difficult to impregnate evenly, and there is a drawback that the light transmittance of the manufactured laminated plate varies.

Furthermore, with the recent improvement in the accuracy of photo solder resist, the conventional ultraviolet region (360-380 nm)
Further, a laminate that blocks light up to a high wavelength region (around 420 nm) is desired, and it is difficult to satisfy the requirement with a conventional ultraviolet absorber or the like.

As a countermeasure, a dye or a pigment is blended at the time of manufacturing the laminate, but such a method has a drawback that the appearance of the laminate differs greatly from the conventional color tone.

[Problems to be solved by the invention]

The present inventor has studied to obtain a laminate having an excellent effect of preventing light transmission while maintaining performance and appearance (color tone) as a conventional laminate for a printed circuit. The present invention has been completed by laminating a prepreg obtained by blending an ultraviolet absorbent that absorbs water with a conventional resin for a laminate on an intermediate layer.

[Means for solving the problem]

The present invention relates to a method for producing a laminated board in which a thermosetting resin is impregnated with a glass fiber base material such as a dried glass woven fabric or a glass non-woven fabric base, and the following general formula ( A method for manufacturing an ultraviolet shielding circuit board, comprising using, as an intermediate layer, one or more prepregs obtained by impregnating a glass woven fabric or a glass nonwoven fabric with a varnish containing 0.1 to 10% by weight of an ultraviolet absorbent described in 1) above. is there.

(Wherein, R ₁ , R ₂ and R ₃ are each C _n H _{2n + 1} and may be the same or different from each other, where n is an integer of 1 to 6). (1) UV absorber
Specifically, 2- (P-methylphenyl) -5-dimethylaminobenzotriazole, 2- (P-methylphenyl) -5-dimethylaminobenzotriazole,
(P-ethylphenyl) -5-diethylaminobenzotriazole and the like are exemplified.

Examples of conventionally commonly used ultraviolet absorbers include salicylic acid, benzophenone, hydroxybenzoate, cyanoacrylate, and benzotriazole, and the like. It is not possible to use a hardening agent or a hardening agent which is decomposed by a hardening accelerator or loses its structure due to its structure being lost.

For example, in the case of a benzotriazole-based compound, the N—H bond that absorbs ultraviolet light is dissociated due to the basicity of amines, and the ultraviolet light absorbing ability is significantly reduced. Therefore, the ultraviolet absorber of the general formula (1) used in the present invention protects the N—H bond by introducing an alkyl group into R, utilizing the action of steric hindrance, further increases the molecular weight, and improves heat resistance. can do. The content of this absorbent is in the range of 0.1 to 10% by weight based on the solid resin content. If it is less than 0.1% by weight, the ultraviolet shielding ability is reduced. It is not preferable because it decreases.

The thermosetting resin used in the present invention is an epoxy resin, a polyimide resin, a phenol resin, a polyester resin, or the like, and is not particularly limited.

〔Example〕

 Hereinafter, Examples and Comparative Examples will be described.

Example-1 Epicoat EP-5046 (brominated bisphenol A epoxy resin manufactured by Yuka Shell Co., Ltd.) 100 parts by weight, dicyandiamide 4 parts by weight, 2-ethyl-4-methylimidazole 0.15 parts by weight, and as an ultraviolet absorber 2- ( 3 parts by weight of (P-methylphenyl) -5-diethylaminobenzotriazole were blended and dissolved with a solvent of methyl ethyl ketone and methyl cellosolve so that the total solid content was 50% by weight. Thus, a glass prepreg having a resin content of 45% was obtained.

One prepreg was placed on the intermediate layer, one prepreg not containing the ultraviolet absorber was placed on the outermost layer, and one 18 μm copper foil was placed on both sides of the prepreg.
Heated and pressed at 90 ° C for 90 minutes at a pressure of 60kg / cm ² and a thickness of 0.6mm
Was obtained.

Example 2 As an ultraviolet absorber, 2- (P-ethylphenyl)-
A 0.6 mm-thick double-sided copper-clad laminate was obtained in the same manner as in Example 1, except that 3 parts by weight of 5-diethylaminobenzotriazole was blended.

Comparative Example 1 A double-sided copper-clad laminate having a thickness of 0.6 mm was obtained in the same manner as in Example except that all prepregs containing no ultraviolet absorber were laminated.

Comparative Example-2 As an ultraviolet absorber, 2-(-2'-hydroxy-
A double-sided copper-clad laminate having a thickness of 0.6 mm was obtained in the same manner as in Example except that 3 parts by weight of 3'-t-butyl-5'-methylphenyl-)-5-chlorobenzotriazole was added.

Next, copper was removed by etching the entire surface of the obtained copper clad laminate, and a photoresist (“PSR-4000” manufactured by Taiyo Ink) was applied to both surfaces of the substrate and dried. A negative film was applied to one side, irradiated with ultraviolet light by an ultraviolet irradiation machine (manufactured by Oak Manufacturing Co., Ltd.), developed with a sodium carbonate solution, and the back exposure was examined by the presence or absence of the remaining resist.

The results are shown in Table 1. As for the substrates of Examples 1 and 2, no back exposure was observed.

The electrical characteristics, heat resistance, and machinability of the laminate used in the examples for printed circuit boards were equivalent to those of conventional laminates.

〔The invention's effect〕

The laminate for a printed circuit obtained by the present invention has the following features.

(1) It has a large shielding effect against light of 350 to 450 nm, and when simultaneously exposing the photoresist applied to both surfaces of the laminate, it is possible to prevent the trouble of exposing the photoresist on the other surface to each other.

(2) By using a prepreg containing an ultraviolet absorber only for the intermediate layer, solvent contamination during circuit formation can be prevented, and it can be used in the same manner as a conventional laminate.

(3) Since the amount of the ultraviolet absorber incorporated into the laminate varnish is small, the electrical properties, heat resistance, and machinability are equivalent to those of the conventional laminate.

Claims (1)

(57) [Claims] 1. A method for producing a laminated board in which a thermosetting resin is impregnated and a glass fiber substrate such as a dried glass woven or nonwoven glass substrate is laminated and formed. A method for producing an ultraviolet shielding circuit board, comprising using, as an intermediate layer, one or more prepregs obtained by impregnating a glass woven fabric or a glass nonwoven fabric with a varnish containing 0.1 to 10% by weight of an ultraviolet absorbent described in 1). (In the formula, R ₁ , R ₂ and R ₃ are each C _n H _{2n + 1} and may be the same or different, where n is an integer of 1 to 6.)